CVE-2021-41823Network attack vector

Cross-site scripting via onmouseover filter bypass

Published Jan 1, 2023 · Updated Apr 11, 2025

Cross-site scripting in the WAF of Kemp LoadMaster 7.2.54.1 allows remote attackers to inject script through crafted onmouseover use. The WAF's XSS filter fails to block certain onmouseover event-handler forms, allowing malicious HTML to pass to a protected application. Execution requires user interaction with the resulting content and permits data access or modification within the browser context.

CVSS severity6.1
Medium
EPSS probability0.49%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in the WAF of Kemp LoadMaster 7.2.54.1 allows remote attackers to inject script through crafted onmouseover use. The WAF's XSS filter fails to block certain onmouseover event-handler forms, allowing malicious HTML to pass to a protected application. Execution requires user interaction with the resulting content and permits data access or modification within the browser context.

The record

CVE
CVE-2021-41823
Published
Jan 1, 2023
Updated
Apr 11, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, CAPEC-63, T1059.007
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 1, 2023CVE publishedPublication date reported by the CVE source.
  2. Apr 11, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
6.1CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CAPEC-63Cross-Site Scripting (XSS)
T1059.007JavaScript/JScript

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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